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[Ext-GDE-44] CCB Response to BDS(gamma-gamma) Change Request of May 17, 2006

Dear Colleagues,

I am announcing that the CCB response, with regards to the latest
Change Request for the Parameter section, is now posted at -


The change request was submitted by A.Seryi on May 17, 2006.
It relates to a likely scenario for the gamma-gamma upgrade of the BDS
and IR to examine in the time-scale beyond RDR.

The requester suggested Class 1 for this request, and after some
discussion CCB agreed to tentatively treat it as Class 1.
G.Blair and T.Markiewicz were assigned as the CCB reviewers.
CCB gratefully acknowledges the comments offered by colleagues
in the CF/S group and members of WWS on the technical issues
and physics implications concerning this change request.

After considerable discussion, however, CCB decided not to accept 
this change request, as is, into BCD. Here is an excerpt from 
the Conclusion section of the CCB response:

1. The CCB expresses its whole-hearted gratitude to the Leaders of 
   the BDS Area Group, Andrei Seryi and his colleagues, for their 
   attempt at examining the gamma-gamma implications to BDS and for 
   offering possible scenarios for revising the BDS to accommodate 
   gamma-gamma running.  

2. However, CCB notes the fact that an outline description does not 
   yet exist for the design studies of the gamma-gamma option within 
   the present BCD. The text offered by the requesters is an important 
   part of it, but, naturally, it does not discuss the full impact of 
   maintaining the gamma-gamma option on the whole of the ILC project.  
   Nor, as is recognized with the R&D to-do list, does it include adequate 
   input from the relevant technical systems for even the BDS specific 

3. In this situation, the CCB cannot accept the proposal, as submitted, 
   into the baseline. It is not appropriate that technical discussion which 
   is part of a major system upgrade with significant changes to facility 
   capability be made unilaterally when the full impact of the change on 
   the rest of the project is not fully known. 

4. Therefore, while again gratefully noting the submission, we hereby 
   return it to the submitters while awaiting further developments on 
   the topic, made in cooperation with the other Area, Global and Technical 
   groups at the appropriate time. CCB suggests that such a taskgroup, under 
   guidance of GDE Executive Committee, could be formed in the TDR time-scale. 

5. CCB also recommends the WWS group to more systematically survey 
   the gamma-gamma upgrade option, including detector integration, 
   possible impact on the interaction region and other related issues, 
   thereby providing GDE with inputs to consider from the physics and 
   detector perspectives. It would be highly desirable if a rough timetable 
   for addressing these issues is made available by the time when RDR becomes 

6. CCB acknowledges the need for reorganizing its scheme for adequately 
   classifying incoming Change Requests on Alternative Configurations or System 
   Upgrade Scenarios.

The full report is available at the URI in the beginning of this
email. BCD web area is located at:


With best regards,

- Nobu Toge (KEK, Accelerator Lab)
  email: toge@xxxxxxxxxxxx
  voice: +81-29-864-5224
  fax:   +81-29-864-3182